Secrecy system for telegraph circuits



J. A. SPENCER SECRECY SYSTEM FOR TELEGRAPH CIRCUITS Filed March 5, 1945 Patented Mar. 19, 1946 SECRECY SYSTEM FOR TELEGRAPH CIRCUITS James A. Spencer, Teaneck, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application March 5, 1943, SerialNo. 478,065

16 Claims.

This invention relates to secrecy systems in telegraph circuits over either radio or wire links. It is of general use in such circuits, but it will be disclosed in connection with telegraph printer installations.

There have been prior systems for maintaining secrecy in telegraph circuits, but these are critical in adjustment and complicated in structure, which makes it difiicult to change the scrambling or decoding plan.

It is an object of the invention to provide a simplified form of secrecy circuit with means for changing the secrecy plan at will.

Another object is to provide phasing circuits to readily put the system into operation.

Other objects of the invention will appear in the following description, reference being had to the drawing, in which:

Figure 1 illustrates the circuits of the invention.

Figure 2 illustrates the tape transmitter.

Figure 3 is a sample telegraph code.

The invention, of course, may be used with various codes, but by way of example I have illustrated it in connection with a system employing the seven unit equal length telegraphic printer code, in which each character has three mark and four space units.

While the invention may be employed in single channels, the system disclosed is of the time division multiplex type. At the transmitting station, the distributors l and 2 will comprise solid rings 3, 4 and segmented rings 5, 6, respectively. The rings of these distributors are shown as broken away, since the portion of the rings allotted to one channel is all that need be illustrated to obtain understanding of my invention. The seven segments of the ring 5 are connected to the tongues T1 to T1, respectively, of a tape transmitter that may be of any design, but I have illustrated a prior art tape transmitter suitable for the purpose. In this transmitter, shown in Fig. 2, a tape I 4, perforated in accordance with the message code signals, controls the engagement of the tongues with either the mark or space contacts M and S, respectively.

Upon energization of the magnet 8, armature 9 is rotated clockwise and the adjustable extension in on the armature arm ll engages projections on code seeker pins I2, of which there are seven. All seven pins are moved downwards and the ends 53 of the three passing through the holes in the tape Hi are removed therefrom. Immediately after this, the lug IS on the arm H ensages lever l5 and rotates it counterclockwise. The opposite end of the lever raises feed ratchet I! by engagement with nuts l8 thereon. The ratchet engages a tooth on wheel [9 and rotates feed roller 2!) forward one step. The pins 2|, passing through feed holes in the tape, advance it one step to the next code perforations. During the downwardmovement, the switch tongues T are moved clockwise by their springs 22 and all seven tongues now engage the space contacts.

Upon de-energization of magnet 8, spring 23 moves the armature 9 back to its former position. Springs 24 likewise return the seeker pins through levers 25, there being seven of these. Only three of the seeker pins will be able to pass through the code perforations in the tape and throw their three cooperating tongues T against the mark contacts M. The remaining four tongues, functioning with the four other seeker pins stopped by the tape 14, will remain in contact with the space contacts S.

When the magnet 8 is de-energizecl, as later explained. spring 26 permits the dog 21, pivoted on ratchet bar ll, to snap over the teeth on wheel l9 as spring 28 returns the ratchet bar to its former position.

It has been found advisable to lock the tape transmitter at times in space position, so as to send out special operating signals to the receiving operator, and this is also done inputting my secrecy system into operation. This locking is accomplished by rotating stop lever 29, rigidly fastened to axle 30, to which is also rigidly fastened lever 3|. One end of spring 32 is fastened to arm 3| and the other end is fastened'tolock arm 33, loosely pivoted on the axle 30.

When the operator desires to stop sending messages from the tape [4, he moves lever 29 clockwise in the direction of arrow a. When arm 3| passes dead center,-spring 32 snaps lock arm 33 counter-clockwise in the direction of arrow 11 against the end of hooked finger extension 34 fastened to armature 9; Then, when magnet 8 becomes energized, the spring 32 further moves lock arm 33 until the end of finger extension 34 enters opening 35 therein. The armature 9 is thus locked in space position and the arm 33 is also locked by the hook as soon as the operating magnet is de-energized. At about the same time, lug 36 engages contact arm 31 and closes contacts 38 in a relay circuit, which opens the circuit of transmitter A and completes the circuit of a special transmittenpermitting the sending of operating instructions only. These latter are not essential parts of this invention. and are not illustrated. The special transmitter and its circuits may be found disclosed in my Patent 2,238,136, April 15, 1941.

When the operator completes the inter-station communication and desires to resume the transmission of commercial messages, stop lever 29 will be rotated opposite to the direction of arrow (1 and when the arm 3| passes dead centeryspring 32 will tend to snap lock arm 33 opposite to the direction of arrow b, but due to the hooked end it can release the armature extension only upon the next energization of the operating magnet? There is thus a definite time for locking and for 1 unlocking the transmitter with the seeker pinsin retracted position, regardless ofthe timethe operator throws the switch 29 for stopping and starting commercial transmission. Springs 24 are then free to move the seeker pins against the tape M or into perforations therein and switch contacts are opened. 3

To provide a scrambling or secrecy arrangement, I employ three tape transmitters: two at the sending station and a third at the receiving station. All three transmitters are alike and may be considered to be the one just described, though, of course, other types may be used. The one designated A on the drawing is the regular message transmitter and the one designated B is the coding or scrambling transmitter, and C is the decoding transmitter at the receiver. The mark and space contacts M and S of the transmitter A are connected to the space and mark contacts S and M, respectively, of transmitter B. The movable tongues |T1 to lT'z, inclusive, of the latter are connected to the contacts on a control switch 39 adapted to be engaged by the movable switch member 40, which is grounded. For. the purpose of explanation, it ma be assumed that the switch member 46 is manually operated.

The tape transmitters A, B and C have operating magnets similar to magnet 8 in Fig. 2, but the switch 31, 38 is not connected in circuit in transmitters B and C. It is used only in th A transmitter. To distinguish the'three magnets in further description, they are designated as 8a, 8b and 8c. 1

The solid ring 4 of the distributor 2 is connected to power, say to the positive terminal. The only segments in the ring 6 having electrical connections are segments No. 8 and No. 9, the former being connected to one terminal 01'- the coil of magnet 8a and the latter to one terminal of magnet 8b. The other terminals of these magnets are grounded.

The ring 3 is connected to the keyer unit, which in this case has been shown as containing a duplex triode 4| controlled by the tape transmitter signals, though, of course, it could comprise two separate tubes or could be any other type of keyer.' The input electrodes or grids of the triode are connected to opposite terminals of the secondary of transformer 42, and the. mid-terminal of this secondary is grounded. The plates of the triode are connected to opposite terminals of the primary of transformer 43 and the midpoint of this primary is connected to the positive terminal 44. The unipotential cathodes of the triode are connected together and to ground through resistance 45, which serves as a controllable negative bias for the keying operation. The cathodes are also connected to the positive terminal 44 through resistance 46. The values of the resistances 45 and 46 are such as to normally produce a blocking negative bias on the grids of the input electrodes of-the duplex triode 4!.

The connections of the heaters for the triode have not been completed, as this is a well-known circuit. The connection from ring 3 is made to a suitable point in resistance 45.

Th primary of transformer 42 is connected to a tone generator 41, of an type.

The secondary of transformer 43 is connected to. the outgoing link 48, which may be either a radio or wire link, as desired.

The link 48 at the receiving end is connected to suitable receiving devices having, for example, a rectangular plus and minus signal output fed to the coil of polar rela 49, having one contact connected to the positive terminal 50 and the other contact connected to the grounded plus-minus terminal, which in this circuit is the negative contact. An incoming signal of one sign throws the tongue against the positive contact and ;a signal of opposite sign throws it against the negative contact. The conversion of the signals to plus and minus currents may be secured by 'any well-known means: for example, by alocking circuit such as disclosed in the pate ent to Richard E. Mathes, 2,214,624, September 10, 1940; also, on and ofi could be substituted by making obvious changes.

The tongue of the polar relay 49 is connected to the solid ring 52 of distributor 53. The segmented ring 54 of this distributor has twice as many segments as the ring 5 at the transmitter, the first three of the additional ones being used for phasing operations. The others are not utilized in this circuit. The segments Nos. 1 to 7 of ring 54 are connected to terminals of seven printer magnets, designated as a whole by reference character 55. The other terminals of thes magnets are joined together and connected to the movable member 56 of a switch 51, similar to the switch 39 at the transmitter. The seven contacts of this switch are connected respectively to the tongues 2T1 to 2T7 of tape transmitter C. The mark contacts M of this transmitter C are connectedto the positive terminal 58. The operating magnet has one terminal connected to i ground and the other terminal connected to segment No. 9 of the segmented ring 59 of the distributor 6B, which is similar to the distributor 2 at thetransmitter. The eighth segment of this distributor is connected to one terminal of the coil of the eighth pulse magnet 6|. terminal of this coil is grounded. The printer may be of any desired type, but by way of example it may be like the printer disclosed in my Patent 2,269,559, January 13, 1942, a full description of which is made therein. An understanding of the printer operation is, however, not necessary for an understanding of this invention.

Brushes 62, 63 rotate at the transmitting station'at a constant speed, to connect the segments of the rings 5 and 6 in succession to their respective solid rings 3 and 4. At the receiver, the brushes 64, 65 rotate at this constant speed, by means well known in the art. The solid ring 66 of distributor 66 is connected to the positive terminal 61.

The segment No. 1a of distributor 53 is connected to one terminal of the coil of relay 68 and to the tongue 69 of this relay. Tongue H1 is connected to ground.

The phasing segment No. 2a of distributor 53 is connected to one terminal of the coil of relay H. The other terminal of the coil is connected to the contact "of relay 6B. This segment No. 2a is also connected to tongue '13 of relay H. The tongue 14 of this relay is connected to ground.

The other- Segment No. 3a of distributor 53 is connected to one terminal of the coil of relay 15. The other terminal is connected to contact I6 of relay H. Tongue Tl of this relay is connected to one terminal of the coil of relay l8 and to the remaining terminal of the coil of relay 68. The positive terminal is connected to the other terminal of coil'l8 and to the contact 19 through appropriate resistances 85!, 8|. The positive terminal is also connected through the resistance 811' to contact 82 of relay 18. Segment No. 9 of ring as is connected through common resistance 83 and separate resistances B4, 85 to contacts 86, Bl of relays B8 and II, respectively, and to tongue 88 of relay l8. Tongue 89 of relay [8 is connected to one terminal of a manual switch or push button 90, the other terminal of which is connected to contact 9! and to ground.

The operation of my improved secrecy system will now be described:

It will be assumed that the switch arms 40 and 56 at the transmitter and receiving stations are placed on the contacts connected to the tongues lTi and 2T1. respectively. All three tape transmitters have been locked in space position by the mechanism of Fig. 2. A tape, perforated in accordance with the message to be transmitted, will be placed in transmitter A. 'An endless band of tape will be inserted in each of the transmitters B and C. The perforations in the latter two tapes may be in accordance with any characters of the code and arranged in any order, as long as the two tapes are perforated identically, but for simplicity it will be assumed that each tape is perforated for the twenty-six letters of the alphabet arranged in order. The B and C tapes should be set with identical characters in operating position which have perforations in the identical positions in which switches MI and 56 are set; for example, with the perforations for the letter Z in position over the seeker pins.

By communicating between the stations through the special transmitter or by any other means, the receiving operator will understand that the system is to be phased for the start of regular transmission. He thereupon will momentarily close switch Qil, which will energize relay 18. This relay will lock up through its holding circuit and transmitter magnet 80 will be energized by closure of the circuits of contacts 82, 33. This energization, however, does not set up a new combination as the armature was already in down position because of the manual lock. The receiving operator then releases the manual lock on the C transmitter. The transmitter C thus remains locked up with the perforations for the letter Z in operative position, by the continued energization of magnet 80 through contacts 82, 88.

The transmitting operator will now move the manual lever 29 (Fig. 2) to unlock transmitter 33, but hook end 3 1 prevents its unlocking. immediately. When the brushes reach the ninth segments, magnet 8b is energized and lock arm 33 clears the hook on the extension 34 and the transmitter is unlocked. This energization, however, does not set up a new combination as the armature was already in down position because of the manual lock. The letter Z thus remains in operative position. When the brushes leave the ninth segments, magnet 8b is de-energized, the seeker pins are released and the first. third and fourth seeker pins pass through the perforations in the tape. This moves tongues [T1, [T3 and lTs against their mark contacts (see code in Fig. 3). i

As the brushes next rotate over the segments Nos. 1 to 7, the circuit is thus set so that mark pulses will be sent out at each segment. At segment No. 1, a portion of resistance 45 will be short-circuited through brush 62, segment No. l, tongue T1, space contact S (transmitter A being locked in space position), mark contact M of transmitter B, tongue lT1, No. I contact, switch arm 40 and ground. This unblocks tube 4! and a tone impulse passes through transformer 43. This pulse will be transmitted by any desired device (not shown). At the receiving station, the tongue of relay 49 will be thrown against the positive contact and a pulse will pass from terminal 50 through brusnB L. segmentNo. 1a,

through the-coil of relay 68, through closed contacts 89, BI and ground. The energization of relay B8 closes its holding circuit and its switches remain closed after the brush passes off of segment No. la. When the brushes are on segment No. 2 at the transmitter and segment No. 2a at the receiver, a similar pulse will be sent out and it will energize relay 1!, which closes its holding circuit. When brushes 62 and 64 pass on to segments Nos. 3 and 3a, respectively, a similar pulse will cause the energization of relay 15. When this relay is energized, it shortcircuits the coil of relay 18 through contacts 11, T9 and the latter is de-energized. The de-energization of relay i8 interrupts the holding circuits through relays 68 and H and de-energizes tape transmitter magnet 80. Both the B and C transmitters are now unlocked with the letter Z in position. They are thus in phase.

When the brushes pass in succeeding cycles on to the ninth segments, magnets 8b and 8c are both energized and their respective tapes are advanced in unison from then on.

. The transmitter operator may unlock transmitter A and start transmission therefrom. Before referring particularly to the action of the tape controls in transmitters B and C, a better understanding of the operation will be obtained by analyzing the action in a general way. There are two conditions, only. that influence the transmission: one, when the grounded tongue of transmitter B is on the S contact; two, when such tongue is on the M contact. Since a mark signal is transmitted when a short-circuit is completed around a portion of resistance 45, it is evident that mark and space signals will be transmitted in the normal way from transmitter A when the grounded tongue of transmitter B is on the S contact; that is, there will be no reversal or scrambling of the signals. At this same time, the tongues connected to switch arm 56 will also be on the S contact. At the receiver, under this situation, the received marks will throw the tongue of relay 49 to the positive contact and since the tongues of transmitter C, like those of transmitter B, will be on the space contacts, which are grounded, the received marks will cause the operation of the selector magnets 55 as they are selectively energized. There will thus be nor mal printing of messages sent out from the transmitter A in the normal way.

When the grounded tongue of transmitter B is on contact M, it is now obvious that the marks from transmitter A will be sent as spaces. The signals are thus reversed. At the receiver, the received spaces will cause the tongue of relay 48 to move to the ground contact. Since the tongue of transmitter C is also on mark contact M, the common return of the selector magnets will be connected to'the positive terminal. The selector magnets will thus be energized. On the other hand, the spaces sent out from trans mitter A, under this situation, will be transmitted as marks. These will cause the tongue of relay 49 to move to the positive contact. This places positive potential on both the terminals of the selector coils and they will not operate. It will thus be seen that the transmitter C decodes or reverses the reversed signals.

It is evident from the foregoing that proper signals are recorded at the receiver irrespective of the reversals 01' non-reversals of the units of the code characters at the transmitter station, but an unauthorized receiver cannot print or otherwise interpret the message, as it is garbled by reversals, the timing of which is unknown to anyone but the authorized operators.

Since it is the grounding action that causes transmitter B to reverse the signals sent from transmitter A, it is obvious that the other tongues in transmitter B have no efi'ect on the operation with this particular adjustment. They, however, have an important function, as any one of them can be made the grounded tongue by moving the switch 40 to engage the contact connected thereto. Thus, the reversing plan can be changed at will tomake synchronous printing of the messages by unauthorized persons practically impossible.

In summary, it may be said that with switches 40 and 56 set on the first contacts, the circuit is set for reversal by transmitter B when the perforations for the letters A, C, D, F, M, T, U, W, Y and Z are in position over the seeker pins. There will, however, be no reversal of the signals of transmitter A when the perforations of the remaining letters of the alphabet are over .the seeker pins.

When the switches 40 and 56 are moved to the second contacts, there will be reversals of the signals when the perforations of letters B, H, I, L, N, O, P, Q, T, U and W appear in position over the seeker pins. Thus, the moving of the two switches changes the secrecy plan. This change can be readily made by special communication between the transmitting and receiving stations, with the transmitters locked as described.

It will be evident from an inspection of Fig. 3 what changes will be made in the reversing action when the switches arethrown to any one of the other remaining seven contacts and this need not be explained.

While I have described my invention, by way of example, with use'of the same code for transmitters B and C as is used for transmitter A, this is not essential. The five unit or any other code could just as well have been used. Furthermore, no particular code or order of characters is required. Random perforations on tapes B and C would produce the same scrambling'effect, but of course the B and C tapes must have identical perforations. If the B and C tapes are not perforated in accordance with any characters of known order, it will be advisable to number the perforations or to indicate the starting point in some way, so that the transmitting and receiving operators can set the tape transmitters in correct positions.

Various modifications may be made without departingifrom the spirit of the invention.

Having described my invention, what I claim is:

1. In secrecy devices for multi-unit equal length code signal systems, a pair of conductors,

a message transmitter, a reversing transmitter, said transmitters having switch tongues and mark and space contacts, means for connecting the mark and space contacts of one transmitter to the space and mark contacts, respectively, of the other transmitter, means for connecting the switch tongues of the message transmitter successively to one of said conductors, means for connecting the other of said conductors to any one of the tongues of the reversing transmitter and disconnecting the other tongues therefrom, a continuous band of tape in the reversing transmitter having predetermined perforations and means operated by said perforations in the tape for controlling the engagement of the tongues of the reversing transmitter with. its said contacts.

2. In secrecy devices for multi-unit equal length code signal systems, a pair of conductors, a message transmitter, a reversing transmitter, said transmitters having switch tongues and' mark and space contacts, means for connecting the mark and space contacts of one transmitter to the space and mark contacts, respectively, of the other transmitter, means for connecting the switch tongues of the message transmitter successively to one of said conductors, means for connecting the other of said conductors to any one of the tongues of the reversing transmitter and disconnecting the other tongues therefrom, a tape in the message transmitter having perforations in accordance with the message to be transmitted, a continuous band of tape in the reversing transmitter having predetermined perforations, means coooperatin with said perforations for controlling the engagement of the tonguesof the transmitters with their respective contacts and means for advancing said tapes once each code character cycle.

3. In secrecy devices for multi-unit equal length code signal systems, a first, a second and a third tape transmitter, each having switch tongues and mark and space contacts, the mark and space contacts of the first transmitter being connected to the space and mark contacts, respectively, of the second transmitter, a transmission circuit, means for connecting the tongues of the first transmitter in succession to a terminal of the sending end of said transmission circuit, means for connecting a selected one of the tongues of the second transmitter to another terminal of the sending end of said transmission circuit, a series of printing magnets,'means for connecting one terminal of the printing magnets to a selected one of the switch tongues of the third transmitter, means for connecting the other terminals of said printing magnets in succession to a terminal'of the receiving end of said transmission circuit and means for connecting the space contacts of the third transmitter to another terminal of the receiving end of said transmission circuit.

4. In secrecy devices for multi-unit equal length code signal systems, a first, a second and a third tape transmitter, each having switch tongues and mark and space contacts, the mark and space contacts of the first transmitter being connected to the space and mark contacts, respectively, of the second transmitter, a transmission circuit, a keying device connected to said circuit, means for connecting the tongues of the first transmitter in succession to one terminal of said keying device, means for connecting a selected one of thetongues of the second transmitter to another terminal of said keying device, a line relay in the receiving end of said circuit'having mark and space contacts and a switch :blade adapted to engage separately therewith a series of :printing magnets, means for connecting one terminal of the printing magnets to a selected one :of the switch tongues of the third transmitter, means for connecting theother terminals :of said printing magnets in succession to said switch blade and :means for connecting the mark and space contacts of the third transmitter to the mark and space contacts of the line relay.

:5. In phasing devices for multi-unit equal length code signal secrecy systems, a tape transmitter-having mark and space contacts and movable switch tongues adapted to engage separately therewith, a transmission circuit, a reversing switch having mark and spacecontacts and a movable blade adapted to engage separately therewith, the mark and space contacts of said transmitter being connected to the space and mark contacts, respectively, of said reversing switch, said blade being connected to a terminal of the sending end of said transmission circuit, means for manually locking said switch tongues and movable blade in conducting relation with their space contacts, means including a potential source for cyclically connecting said switch tongues in succession to another terminal of the sending end of said transmission circuit, whereby space signals are sent over said transmission circuit when said tongues and blade are simultaneously in conducting relation with either said space contacts or said mark contacts, respectively, and for sending mark signals thereover when the tongues and blade are simultaneously in conducting relation with either the mark and space contacts or the space and mark contacts, respectively, a printer selector magnet for each code unit, means for connecting the receiving end of said transmission circuit to said selector magnets in succession, an electromagnetic switch being included in said last-mentioned means adapted when energized to hold its movable member in signal space position, means for energizing said electromagnetic switch, means for de-energizing said electromagnetic switch upon receipt of mark signals over the transmission circuit .and means for moving the blade of the reversing switch into conductingrelation with the mark contacts of the tape transmitter at a predetermined time in said cycle.

6. In phasing devices for multi-unit equal length code signal secrecy systems, a tape transmitter having mark and space contacts and movableswitch tongues adapted to engage therewith, a transmission circuit, a reversing switch having mark and space contacts and a movable blade adapted to engage therewith in its alternate positions, the mark and space contacts of said tape transmitter being connected to the space and mark contacts, respectively, of said reversing switch, said blade being connected to a terminal of the sending end of said transmission circuit, means for'locking said switch tongues and movable blade in conducting relation with their space contacts, means including a potential source for cyclically connecting said switch tongues in succession to another terminal of the sending end of said transmission circuit, a printer selector relay for each code unit, means including an electromagnetic switch for connecting the receiving .end of said transmission circuit to said selector relays .in succession, adapted when energized to hold its movable member in signal space position, means for energizing said electromagnetic switch, means for ole-energizing said electromagnetlc switch upon receipt of mark signals over the transmission circuit and means *forireleasing'the lockingmeansof said reversing'switch and moving the blade ontoitsmarkmontacts at a predetermined'timein said cycle.

7. In phasing devices for multi-unit equal length code signal'secrecy systems, atapextransmitter having mark and space contacts -and;movable switch tongues adapted to engage'therewith in their alternate positions, a transmission circuit, a reversing switch having mark and space contacts and a movable blade adapteditoiengage therewith, the mark and space contacts of said tape transmitter .being connected to the space and mark contacts, respectively,'of aid reversing switch, said blade being connected to a terminal of the sending end of said transmission circuit, means including 'a potential source for .cyclicly connecting said switch tongues in succession'to another terminal of the sending :end o'fsaidtransmission circuit, a printer selector relay for each code unit, means for connecting :th receiving end of said transmission circuit to said selector relays in succession, an electromagnetic switch being included in said last-mentioned means adapted when energized to'hold its movablesmemher in signal pace position, means for energizing said electromagnetic switch, means :for cieenergizing said electromagnetic switch uponzreceipt of mark signals over the transmission circuit and means for moving the blade of the reversing switch into conducting'relation with the markcontaots of the'tape transmitter at apredetermined time in said cycle.

8. In phasing devices for multi-unit equal length code signal secrecy systems, a message and a reversing tape transmitter, each having mark and space contacts and movable switch tongues adapted to engage therewith, the mark and space contacts of one tape transmitter being connected to the space and mark contacts, respectively, of the other, a transmission circuit, a switch tongue of the reversing transmitter being connected 'to a terminal of the sending end of said transmission circuit, means includinga potential source for cyclicly connecting the switch tongues of said message transmitter insuccession to another terminal of the sending end "of said transmission circuit, a printer selector relay :for each code unit, a second reversing tape transmitter having space and mark contacts and switch tongues adapted to engage separately therewith. means for connecting the receiving end of said transmission circuit to said selector relaysin succession throughia tongue of said second reversing tape transmitter, an electromagnet adapted when energized to hold the tongues of the second reversing tape transmitter-against their space-contacts, means for energizing said electromagnet, means for de-energizing said electromagnet upon receipt of mark signals over the transmission circuit and means for moving the tongues of the first-mentioned reversing tape transmitter against their mark contact at a predetermined time in said cycle.

9. In phasing devices for multi-unit equal length code signal secrecy systems, a message and a reversing tape transmitter, each having mark and space contacts and movable switch tongues adapted to engage separately therewith,the mark and space contacts of one tape transmitter being connected to the space and mark contacts, respectively, of :the other, a transmission circuit, a switch tongue of 'the reversing transmitteribeing connected .to :a terminal of thesending end of ,said transmission circuit, means includinga potential source for cyclicly connecting the switch tongues of said message transmitter in succession to another terminal of the sending end of said transmission circuit, a line relay. connected to the receiving end of said transmission circuit, said line relay having a pair of contacts and a switch tongue adapted to engage therewith'in its alternate positions, a printer selector relay for each code unit, a econd reversing tape transmitter having a plurality of pairs of juxtaposed contacts and a switch tongue for each pair adapted to engage separately therewith, said juxtaposed contacts being connected to the contacts of said line relay, means for connecting the tongue of said line relay through said selector. relays in succession to a tongue of said second reversing tape transmitter, an electromagnet adapted when energized to hold the tongues of the second reversing tape transmitter against one of their contacts, means for energizing said electromagnetnmeans for de-energizing said electromagnet upon receipt of mark signals over the transmission circuit and means for moving the tongues of the first-mentioned reversing tape transmitter against their mark contacts at a predetermined time in said cycle.

10. In receivers for multi-unit equal length code signal secrecy systems having the signals in the transmission circuit reversed at predetermined times, a printer selector relay for each code unit, a tape transmitter having space and mark contacts and switch tongues adapted to engage separately therewith, said space contacts being connected to a terminal of the receiving end of said transmission circuit, means for connecting another terminal of the receiving end of said transmission circuit through said selector relays in succession to a tongue of said tape transmitter,

an electromagnet adapted when energized to-hold" the tongues of the tape transmitter against their space contacts, means for energizing said e1ec-- tromagnet and means for de-energizing said electromagnet upon receipt of mark signals over the transmission circuit.

11. In receivers for multi-unit equal length code signals reversed in accordance with the marks of a succession of predetermined code characters, a line relay having mark and space contacts and a switch blade adapted to be moved into engagemerit therewith upon receipt of mark and space signals, a printer selector relay for each code unit, a. tape transmitter having a pair of mark and space contacts for each code unit and a switch tongue for each pair adapted to engage separately therewith, means for connecting the mark and space contacts of said tape transmitter to the mark and space contacts, respectively, of said line relay, a tape perforated in accordance with said succession of code characters for controlling the engagement of said switch tongues with said mark and space contacts and means for connecting said switch blade to one of said switch tongues through said selector relay in succession.

12. In receivers for multi-unit equal length code signals reversed in accordance with the marks of a succession of predetermined code characters, a line relay having mark and space contacts and a switch blade adapted to be moved into separate engagement therewith, a printer se1ector relay for each code unit, a tape transmitter having a pair of mark and space contacts for each code unit and a switch tongue for each pair adapted to engage separately therewith, means for connectingthe. mark and space contacts of gizing said electromagnet after said tape transmitter to the mark and space-con tacts, respectively, of said line relay, a tape perfo-- rated in accordance with said succession of code characters for controlling the engagement of said switch tongues with said mark and space contaets; a movable selector arm adapted to separately engage certain of said switch tongues and means for connecting. said switch blade to said selector arm through said selector relays in succession. V

13. In receivers for multi-um't equal length code signals reversed in accordance with the marks of a succession of predetermined code characters, a line relay having a pair of contacts connected to a potential source and a switch blade adapted to be moved into engagement with the one or the other upon receipt of mark and space signals, a tape transmitter having a plurality of pairs of mark and space contacts and a switch tongue for each'said pair adapted to engage separately therewith, a plurality of timing relays, an electromagnet, means for momentarily energizing said electromagnet'once each code character cycle, said electromagnet having an armature, means for advancing said tape to a new code character by movement of said armature upon energization of said electromagnet, means for producing prolonged energization of said electromagnet, means for closing a break in the circuit of a first one of said timing relays, means for successively closing breaks in the circuits of the remaining timing relays after energization of the first timing relay, means for connecting said blade in succession to said relays and means controlled by the last relay for de-enerthe said prolonged energization thereof.

14. In receivers for multi-unit equal length signals, a tape transmitter having a pair of mark and space contacts for each code unit and a switch tongue for each said pair of contacts adapted to engage separately therewith, a first timing relay, a second timing. relay, means controlled by the first timing relay for closing a break in the circuit of the second timing relay, an electromagnet, means for momentarily energizing said electromagnet once each code character cycle, said electromagnet having an armature, means for advancing said tape to a new code character by movement of said armature upon energization of said electromagnet, means for producing prolonged energization of said electromagnet, means for closing a break in the circuit of the first timing relay, means for connecting said blade in succession to said first and second relays and means controlled by said second relay for de-energizing said electromagnet after prolonged energization thereof.

15. In receivers for multi-unit equal length code signals reversed in accordance with the marks of a succession of predetermined code characters, a line relay having a pair of contacts connected to a potential source and a switch blade adapted to bemoved into engagement with the one or the other contact upon receipt of mark and space signals, a tape transmitter having a plurality of pairs of mark and space contacts and a switch tongue for each said pair adapted to engage separately therewith, a first timing relay, a second timing relay adapted to have a break in its circuit closed by the first timing relay, a third timing relay adapted to have a break in its circuit closed by the second timing relay, an electromagnet, means for momentarily energizing said electromagnet once each code character cycle, said electromagnet having an armature, means for advancing said tape to a new code character by movement of said armature upon energization of said electromagnet, means for producing prolonged energization of said electromagnet, means for closing a break in the circuit of the first timing relay, means for connecting said blade in succession to said first, second and third relays and means controlled by said third relay for de-energizing said electromagnet after thesaidprolonged energization thereof;

characters, a line relay having a pair of contacts connected to a potential source and a switch blade adapted to be moved into engagement with the one or the other upon receipt of mark and space signals, a tape transmitter having a plurality of pairs of mark and space contacts and a switch tongue for each said pair adapted to engage separately therewith, a plurality of timing relays, an electromagnet, means for momentarily energizing said electromagnet once each code character cycle, said electromagnet having an armature, means for advancing said tape to a new code character by movement of said armature upon energization of said electromagnet, means for producing prolonged energization of said electromagnet, means for successively closing breaks in the circuits of the timing relays, means for connecting said blade in succession to said relays, means controlled by energization of the last relay for de-energizing said electromagnet, means 

